Former New York City Mayor Michael Bloomberg — a onetime moderate Republican who has crusaded on gun control —- is considering throwing $1 billion of his vast fortune into an independent bid for president, according to several sources familiar with his plans.

He has set March as a deadline, according to one, and his decision will likely be contingent on the results of early primaries, and he's more likely to take the leap if the "extremes" — meaning Trump, Ted Cruz or Democrat Bernie Sanders — prevail.

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"If you have a Democratic front-runner who is opposed to capitalism, and a Republican front-runner who wants to deport 10 million immigrants, yeah, that'll make a difference," said the person, who has direct knowledge of his preparation, which includes polling and message-testing.

Another Bloomberg associate familiar with the former mayor's plans put the likelihood of an actual run between 30 percent and 50 percent.

“I wouldn’t say he is leaning toward,” the source said, adding that Bloomberg has been “looking harder and harder” at the possibility of testing his chances as the race has become more fractured. “It’s gone from idle chitchat to ‘let’s take a real look.’”

“A lot of people on a daily basis tell him, ‘you should do it.’" the source said. "I think he’s been watching and toying with it for a while.”

Bloomberg would be less interested in running if Hillary Clinton or a more moderate GOP candidate emerges from the early contest, two sources in Bloomberg's circle told POLITICO. In 2013, he reportedly urged her to consider running for New York City mayor and succeeding him.But one of the insiders added that part of Bloomberg’s thinking now is that if Clinton becomes the party’s nominee and a Department of Justice probe leads to a federal indictment, that would undermine her ability to serve.

The former mayor was raised in a Democratic family outside of Boston and contributed to Democratic campaigns as a young man. But he always viewed the two-party system as a political Uber — a convenient means of getting where he wanted to go that commanded little personal allegiance — and ran for mayor under the Republican banner only because it offered him an easier path to nomination.

Bloomberg’s exploration of a bid, first reported in The New York Timeson Saturday, is motivated by his belief that the ascent of Trump, a fellow billionaire who the business information executive has known for two decades, represents a crisis in the two-party system that calls for a third-party solution. But he's equally wary of Sanders, a Democratic socialist who has called for the breakup of big Wall Street banks — the target consumers of Bloomberg's multibillion-dollar business metrics service.

Bloomberg has become increasingly agitated by the "tone and tenor" of the campaign so far but is realistic about his chances, people close to him say. He has discussed a number of potential strategies with a collection of advisers and friends — including the possibility of concentrating his immense resources on a single state like Florida, which both major-party candidates need — to leverage changes in policy.

Even if he doesn't run, the mere mention of his billion-dollar bid would have a ripple effect. The front-page splash on the home page of the Timesmirrors a similar gambit he undertook eight years ago, with little effect. In January 2008 — as Barack Obama and Clinton dueled it out New Hampshire — Bloomberg hosted a bipartisan summit of moderates in Oklahoma designed to raise attention for his cause, but ultimately it underscored his marginalization from the national political conversation.

The three-term former mayor, who governed with a middle-of-the-road philosophy of social liberalism and low-tax conservatism, has struggled to gain political traction since leaving office in 2013. Bloomberg, 73, spent tens of millions in an unsuccessful bid to toughen the nation’s gun control laws in the wake of the Newtown, Connecticut, school shootings — and many gun rights activists claim his name alone created a backlash that helped sink his cause.

Even if Bloomberg carries out his promise to serve as his own super PAC, the odds of his winning are steep, verging on impossible. He would most likely serve as a spoiler in Northeastern states, and potentially Florida, which has a large Jewish population — and he’s just as likely to draw votes from the Democratic nominee as the Republican pick, whether it’s Trump or anyone else.

During his mayoralty, Bloomberg surrounded himself with a stable of well-regarded political operatives with deep connections in Democratic circles — former Hillary Clinton aide Howard Wolfson and Kevin Sheekey, a former staffer for late New York Sen. Pat Moynihan who was recently considered as a possible chief of staff to Vice President Joe Biden.

And many of his loyal former aides are eager for him to step back into the political ring. “A lot of people who worked for him in the past believe he has more to contribute and want to be a part of it,” a Bloomberg associate said.